Projects which have been underway include the following: A. Methods to produce consistent preparations of liposome-entrapped Melphalan: Liposomes or phospholipid vesicles have been used experimentally as a biodegradable carrier of cytotoxic drugs. Previous studies had shown that S.C. injection of liposomes containing Melphalan (MPL), a cytotoxic drug effective against mammary cancer, may be useful in treating lymph node metastases because lymphatic capillaries preferentially absorb fatty substances. A technique was developed in which the optical density of the liposome preparation was monitored as a function of sonication time and liposome size. The electron microscope was used to assess the morphology and size of the vesicles. Prolonged sonication produced liposomes that S.C. gave high and sustained concentration of MPL in lymph nodes of the rat; B. Mechanisms of in vitro tubulin polymerization induced by nucleotide analogs of GDP and GTP: Understanding the role of nucleotides in tubulin polymerization may aid in the design of effective cancer drugs since tubulin is a major component of the mitotic spindle which is intimately involved in cell division. The electron microscope was utilized to examine negative stains of tubules or thin sections of pelleted polymer material. These studies demonstrated that many nucleotide analogs of GDP and GTP supported polymerization; C. Ultrastructural characterization of malignant human cell lines maintained in vivo in athymic host systems. Our laboratory has established several human melanomas as xenografts in nude mice. Two of these melanomas (LOX and SESX) form metastases in the lungs of nude mice. This provided a means of investigating the mechanisms influencing lung colony formation. Samples from various sublines of LOX and SESX were examined in the electron microscope and several morphological features noted. Large amounts of intracytoplasmic filaments were particularly apparent in S.C. tumors of LOX and SESX. Cells of brain-passed tumors were observed as having numerous electron dense deposits within the cytoplasm. These and further observations may help explain the unusual metastatic behavior of these melanomas.